1. Field of The Invention
The present invention relates to a zero insertion force socket having a cover movable with respect to a base thereof, particularly one which has top loading contacts cooperating with relatively narrow openings of passageways for prevention of unwanted solder sputtered to any other portion than the solder tail of the contact.
2. The Prior Art
Zero insertion force (ZIF) sockets have been used to connect a CPU to a printed circuit board for years. Normally, this socket needs a relatively long pitch for accommodating a lead-in distance of each contact which allows a corresponding CPU pin to be inserted into the socket with substantially zero insertion force firstly and then moved by a cover of the socket for this lead-in distance to abut against contacting portion of the contact in the socket. These sockets may be referred to U.S. Pat. Nos. 5,057,031 and 5,730,615. For effectively utilizing the space of the socket and lowering the profile thereof a low profile socket in U.S. application Ser. No. 09/146,998 has been proposed which belongs to the same assignee of this application. Although this configuration works well in many aspects, a portion of the contact other than the solder tail thereof is apt to be attached with solder sputtered during a soldering procedure. This unwanted solder when retained in the base of the socket is apt to negatively affect the operation of the socket. The reason causing the unwanted solder retained in the base is in that the contact is a bottom loading type which needs a relatively large opening at the bottom of the base for entrance of the contact during assembling of the contact into the base. Referring to FIGS. 4 and 5, a conventional contact 4 comprises an engagement plate 41 from which a stationary contacting portion 44 extends upward, a curved portion 45 connected to the stationary contacting portion 44, and a movable contacting portion 46 connected to the curved portion 45 and facing inward the stationary contacting portion 44. The contact 4 is loaded into a passageway 50 of a base 5 from a bottom opening 60 thereof. The engagement plate 41 has barbs 411 formed in two ends thereof for engagement with inner walls 55 (only one is shown) of a corresponding passageway of a base 5. The movable contacting portion 46 is forced to expand outward by the CPU pin when the CPU pin is driven by the cover of the socket to move for the lead-in distance within the contact. A solder tail 43 extends substantially perpendicular to the engagement plate 41 for attachment of a solder ball thereto. It can be seen that after the contact 4 has been configured in the passageway 50, relatively large space may exist in the opening 60 which constitutes a path for sputtered solder to attach to other portions of the contact 4 other than the solder tail 13 thereby causing problem as mentioned. It is requisite to provide a new structure of the contact and the passageway by which the unwanted sputtered solder is prevented from attaching to those portions other than the solder tail of the contact.